Method and apparatus for treatment of liquid wastes

ABSTRACT

A method and apparatus are provided, wherein liquid waste containing a mixture of organic and inorganic materials or organometallic compounds is, in turn, dehydrated, concentrated, combusted and the ash produced therefrom is recovered in the form of an aqueous solution or a slurry. According to the above method, the high temperature combustion exhaust gases are injected into water in a recovery vessel and the ash entrained therewith is recovered as an aqueous solution or a slurry, and the heat contained in the liquid waste as well as the heat evolved from the auxiliary combusting fuel are recovered in the form of steam which contains non-condensable gases that are utilized in the concentration of additional liquid waste under a reduced pressure.

United States Patent 'Akune et a1.

[ Nov. 12, 1974 METHOD AND APPARATUS FOR TREATMENT OF LIQUIDWASTES [75] Inventors: Mikio Akune, Yokosuka; Kokichi Yoshii, Shibukawa; Tadashi Yamauchi, Kawasaki, all of Japan [73] Assignee: Nittelsu Chemical Engineering Co.,

Ltd., Cheyoda-ku, Japan [22] Filed: June 3, 1971 21 Appl. No: 149,667

- [30] Foreign Application Priority Data June 6, 1970 Japan 45-48852 [52] US. Cl..... 159/4 A, 159/16 A, 159/47 WL, 261/112 [51] Int. Cl Bold l/l4, BOld 47/00, BOld 1/16, B01d 1/00 [58] Field Of Search 159/4 A, 16 A, 47 WL, 261/22, 112; 23/262; 162/30 [56] References Cited UNITED STATES PATENTS 2,303,811 12/1942 Badenhausen 23/262 2,354,175 7/1944 Wilcoxson 2,614,652 10/1952 Su|tzer 23/272 X 2,936,215 5/1960 Hochmuth 23/48 3,309,262 3/1967 Copeland et a1 3,439,724 4/1969 Mason 3,560,329 2/1971 Nelson et al 162/30 X COMPRESSED AIR 1O 2,155,633 4/1939 Bacchi 23/275 2,249,192 7/1941 Titlestad et al... 23/307 2,325,566 7/1943 Wiley et al 23/307 2,524,753 10/1950 Betts 23/48 2,839,122 6/1958 Laquiharre 159/4 A 3,053,615 9/1962 Steinert 159/4 A X 3,153,609 10/1964 Markant et a1... 162/36 3,275,062 9/1966 Williams [59/4 A 3,322,181 5/1967 Williams 159/4 A 3,638,708 2/1972 Farin 159/4 A X Primary Examiner-Jack Sofer [5 7 ABSTRACT A method and apparatus are provided, wherein liquid waste containing a mixture of organic and inorganic materials or organometallic compounds is, in turn, dehydrated, concentrated, combusted and the ash produced therefrom is recovered in the form of an aqueous solution or a slurry.

3 Claims, 2 Drawing Figures on stem WATER, I

AUXILIARY 12 come. FUEL 13 l L aunnen C0 A L11 2g AIR INLET J (SPRAY NO'ZZLE FURNACE- 22 RECOVERY 21 C vessuw l 1 3 5 A 25 RECOVERED I 9 T T DISSOLVED l I MATERIAL e g s l 2 o EVAPORATOR Sc UBBER CONCENTRATE STORAGE LIQUID WASTE STORAGE PATENTLL :mv l 21914 3.841.713 SHEET 10F 2 Fig- I aunnsn 9 fSPRAY NOZZLE .COMPRESSED AIR OR STEAM WATER v AUXILIARY COMB. FUEL\ AIR INLET Furnacenscdvcnv EVAPORATOR CONCENTRATE STORAGE VESSEL 19 RECOVERED DISSOLVED MATERIAL LIQUID WASTE STORAGE METHOD AND APPARATUS FOR TREATMENT OF LIQUID WASTES- BACKGROUND The present invention relates to a method wherein liquid waste containing a mixture of organic and inorganic substances or organic metallic compounds is, in turn, dehydrated, concentrated and combusted and the ash produced therefrom is recovered as an aqueous solution or a slurry.

In general, it is known that the temperature at which the organic materials can be burned should be of the, order of 800 C or above.

Where the liquid waste contains small amounts of organometallic substances, such as for example sodium carboxylate, it is required to evaporate a great amount of water and to raise the combustion temperature to well over 800 C, thus consuming a great amount of auxiliary combustion fuel. In this case, it is not advantageous, from a heat economy viewpoint, to exhaust to the atmosphere combustion gases having a temperature as high as 800 C. Furthermore, this may create a secondary atmospheric pollution problem, that is, sodium carbonate released during the combustion could be contained in the exhaust gases in the form of fine particles.

It has now been found that considerable savings in the consumption of the auxiliary combustion fuel can be attained by combusting the liquid waste at a temperature greater than 800 C, after said waste has been dehydrated and concentrated and the water content has been substantially reduced.

It has further been found that the partial utilization of the heat contained in the combustion exhaust gases for concentrating additional liquid waste will contribute to greater savings in auxiliary combusting fuel, because of the exhaust gases considerable temperature, and in the volume of the furnaces required.

SUMMARY An object 'of the present invention is to provide a method and a system for treating liquid waste containing a mixture of organic and inorganic substances or organo-metallic compounds by, in turn, dehydrating, concentrating and combusting it and recovering the ash produced therefrom as a slurry and utilizing the high temperature combustion exhaust gases for concentrating additional waste.

A further object of the present invention is to provide a method and system for treating liquid waste, wherein the heat evolved from the waste and from the auxiliary fuel is recovered in the form of steam, which is then utilized for reducing the water content of the waste, thus saving in auxiliary fuel consumption.

These and other objects of the present invention will be apparent from the following description.

in the exhaust gases may partly be directly utilized for such purposes in an efficient manner.

A first embodiment of the present invention provides therefore a method wherein the high temperature combustion exhaust gases are divided into two parts, one of which is injected into a recovery vessel to recover the. ash in the form of an aqueous solution or'a slurry, and the other is injected into the waste. to concentrate the same prior to combusting it.

As an alternative it is possible to recover an even greater part of the solid content of the combustion gases in the form of an aqueous solution or a slurry by directly injecting the combustion exhaust gases into the recovery vessel in the form of foams.

When the combustion gases are injected into the recovery vessel, they liberate and give. up their heat to the water during their refloating movement to the water surface, thereby evaporating a great amount of water, and therefore they can be discharged together with a great amount of steam.

Consider for example, the case where the concentration of recovered sodium carbonate solution is desired to be 15 percent, the water to besupplied should consist of the water and steam necessary to obtain said 15 percent sodium carbonate solution. In a method where the combustion gases are directly injected into water, there may take place a decrease in the boiling point of the exhaust gases issuing from the 15 percent sodium carbonate solution, because they contain noncondensable gases such as a nitrogen or carbon dioxide, the temperature being in the range of .85" to- 95 C.

The exhaust gases of this kind contain about percent steam therein, thus affordingconsiderable heat economy when utilized for concentrating the waste.

It is also feasible to concentrate the waste by means of an evaporator incorporating a heat exchanger in which the heat conductiontakes place through indirect contact of the waste with the exhaust gases whichcontain about 60 percent steam.

At normal atmospheric pressure, it is impossible to effect the concentration of the waste, because the temperature of the exhaust gases is lower than the boiling point of the waste. Therefore, to effect the concentration, it is necessary to reduce the pressure of the waste by means of vacuum devices such as a water or steam ejector.

The liquid waste, after concentration by reduction of its water content, is then supplied to a combustion furnace, whereby the auxiliary fuel consumption-is greatly reduced. 7

In general, although dependent on the kinds of solutes, when theconcentration of a-solution containing a mixture of organic and inorganic materials andlor-organo-metallic compounds fallsin the range of 40. to 60 percent, a slurry will result or the viscosity of the solution will increase considerably thus preventing. spraying or injection of the solution into a furnace. Therefore, it is important to hold the'concentration-of the solution within a range which permits its continuous injectionin the furnace. This is done by adjusting the degree of vacuum.

It is advantageous to scrub the exhaust gases exiting from the concentrator before discharging to the atmosphere, because of the possible presence of polluting solid particles entrained therein.

DETAILED DESCRIPTION The following description of the invention is given with reference to the accompanying drawings, in which:

FIG. 1 is a flow diagram of a first embodiment of the invention showing a liquid waste treatment system according to this invention; and

FIG. 2 is a flow diagram of another embodiment of the present invention.

In the drawings, like reference characters designate similar parts.

Referring now to FIG. 1, a liquid waste storage tank (1) is in fluid communication via pump (2) and pipe (a) with a jacket (4) provided in the upper portion of a concentrator or evaporator (3). Provided in the interior of the evaporator (3) is a downcomer (5) to which the liquid waste is introduced. The overflow of the concentrated solution from the evaporator (3) is delivered into a concentrated solution storage tank (6) by way of pipe (b). A pump (7) conveys the concentrated solution from storage tank (6) via pipe (c) to a spray nozzle (9) provided on combustion furnace (8). Compressed air or steam under a medium pressure is introduced into the nozzle (9) via conduit (10) to accelerate the combustion of organic substances in the waste and the evaporation of the water contained therein.

A blower (11) is provided so as to supply to combustion furnace (8) the air required for combustion of the waste concentrate, said blower being connected by way of a pipe (d) with a burner (14) and by way of a pipe (g) to the spray nozzle (9). The auxiliary combustion fuel is contained in a storage tank (12), and via pump (l3) is delivered to burner (14) mounted on the furnace (8). Beneath the furnace (8) is a recovery vessel (15) to receive the combustion exhaust gases produced. A downcomer (18) is disposed inside the recovery vessel, which is provided also with a header (17) through which water introduced via pipe (16) is supplied to the recovery vessel (15).

The recovery vessel (15) is connected to a recovered waste storage tank (19) through a pipe (e), and the combustion gases are exhausted through a duct (20) located in the upper portion of the recovery vessel.

Approximately one-half of the combustion gases discharged from the furnace (8) is delivered via duct (21) to downcomer (5) to heat the waste delivered by jacket (4). Connected with the evaporator (3) is a duct (22) to discharge the combustion gases from the evaporator. Valves (23) and (24), provided in ducts (20) and (22), which ducts join in (1), Serve to adjust the volume of the combustion gases being delivered to the evaporator (3). Scrubber (25) is in communication with an exhaust tower (26) and with a water supply via pipe (16).

Turning now to FIG. 2 which shows another embodiment of the present invention, the evaporator (3) concentrates the waste delivered by pump (2). Storage tank (6) connected with the evaporator by pipe (b) contains therein the waste concentrate overflowed from said evaporator.

In this embodiment, all the combustion gases from the furnace (8) are directed to the downcomer (18) in the recovery vessel (15) and then supplied to evaporator (3) by way of an overhead pipe. In communication with evaporator (3) is a condenser (27) to condense the steam evaporated from the waste in the evaporator.

Condenser (27) is connected to another condenser (29) by way of an ejector (28). The condenser (29) is similarly connected to an ejector (30). Condensers (27) and (29) and ejector (30) each communicate with a sewerage tank (31) where the condensed water is introduced. The ejectors (28) and (30) each communicate with a duct 10), and the condensers (27 and (29) are connected to water pipe (16).

OPERATION OF THE SYSTEMS In operation, the liquid waste contained in storage tank (1) is delivered by pump (2) to the downcomer (5) via jacket (4) provided on the upper portion of the evaporator (3) and then concentrated therein, and delivered to the waste concentrate storage tank (6). The concentrate from the storage tank (6) is delivered by pump (7) to the spray nozzle (9) mounted on the furnace (8) and then spray-injected into the furnace for burning. It is preferable to use steam or compressed air as the atomizing source necessary for spraying. The compressed air is led through duct (10) to accelerate the combustion rate of the organic substances contained in the waste as well as the evaporation rate of the water in the concentrate.

The air necessary to support the combustion of the organic substances is supplied by the blower (11) and the auxiliary combustion fuel from storage tank (12) is supplied by pump (13) to the burner (14) of furnace (8).

In the event that the waste has self-sustaining combustibility, the auxiliary fuel is not required, but in general, aqueous solutions such as the waste of carboxylic acid solution do not provide self-sustaining combustibility, thus requiring the auxiliary fuel. It is possible to make the furnace size compact and maintain a stable flame by using a high-load short-flame burner. The temperature of the flame from the auxiliary fuel burner is as high as 1,600 to l,800 C, so that it may effect a rapid evaporation of the water as well as a complete combustion of the organic substances contained in the waste.

It is commonly accepted that the organic materials, in general, can be burned completely at a temperature of over 800 C. On combustion of the waste, the metallic compounds contained in the waste may be obtained as ash and if sodium carbonate is present, this will be released as a portion of' the ash. The melting point of the sodium carbonate being about 850 C, the molten sodium carbonate tends to adhere to the inner surface of the furnace when combustion is carried out at a temperature below 850 C, thus causing clinkers.

In this case, therefore, the combustion temperature should be set at about 950 C. In case of inorganic materials such as sodium chloride, the melting point of the ash will be considerably lower, and thus no damage to the furnace will occur, when combusting at 850 C.

One half of the combustion gases thus produced is injected into the receovery vessel (15) and the remaining half is injected into the evaporator (3). Water is then supplied to the recovery vessel from the downcomer (18) via water pipe (16) and header (17).

Most of the sodium carbonate produced during combustion flows in the molten state along the inside of the furnace walls into the recovery vessel (15). and goes then into solution. Part of the sodium carbonate, in the form of particles, is entrained with the combustion gases into the recovery vessel directly. In this manner,

90 percent or more of the sodium carbonate may be absorbedinto solutionin the'recovery vessel.

The combustion gases are injected into the recovery vessel at about 950 C and then discharged therefrom through duct (20) at a temperature of 90. to 100 C.

As an illustrativeexample,. the rate of flow of waste used with such asystem contained a mixture of, inter alia, organic materials (1,320 lbs/hr), caustic soda (572 lbs/hr) and water 7788 lbs/hr), for a total flow of 9,680 lbs of waste/hr with a calorific value of about 7,215

BTU/lb. Y

The rate of the sodium" carbonate produced during the combustion of thewaste was 759 lbs/hr and about 682 lbs/hr of the sodium carbonate was absorbed in the recovery vessel. Thismeans that about 5,500 lbs/hr of water was evaporated in the recovery vessel. To obtain l0 percent sodium carbonate solution in the recovery vessel, about 11,660 lbs/hr of water should be supplied thereto toobtain about 6,8 20'lbs/hr of percent solution of sodium carbonate.

The sodium carbonate solution thus recovered is stored in a recovery solution storage tank (19) for other applications. I

On the other hand, the remaining one half of the combustion exhaust gasesin injected into the evaporator (3) through duct (21).

With the waste being injected into the evaporator through jacket (4), the waste is brought into contact with the combustion gases. .This effects the evaporation of the water contained in thewaste, and the wastemay be thus concentrated. At this'stage, 5,500 lbs/hrof water is evaporated, and 4,180.1bs/hr of the concentrate may be stored inthe storage tank (6).

As shown in FIG. 1, if a partof thecombustion gases is bypassed to the evaporator, a majority of the sodium carbonate produced in thefurnace will. be led into the recovery vessel ('15), so'that'the amount of the particulated sodium carbonate contained in the combustion gases and eventually introduced into the evaporator, will be greatly reduced, thereby precluding the carbonate from accumulating in the concentrated waste.

The controlin the concentration of the waste can be effected by adjusting botlr valve-(23) in duct and valve (24) in duct (22-). The volume of the combustion gases to be injected into the evaporator is thus also eventually adjusted If the combustion gases are entirely injected into the waste to concentrate .it, the sodium carbonate produced in the furnace will be entirely dissolved in the waste, thereby raisingthe concentration of sodium carbonate therein which, in turn causes the formation of crystals and leads to the formation of a slurry. This will prevent the waste from being readily pumped to the furnace and will interrupt the normal combustion therein.

, To maintain a continuous concentration by means of direct contact between high temperature exhaust gases and the waste, it would be necessary to inject a part of the exhaust gases into an aqueous solution e.g., water, rather than directly into the waste, while the remaining gases are injected in the wastefor concentration purposes.

As it may be apparent from the system of the embodiment shown in FIG. .2, the furnace may be mounted vertically or horizontally on the recovery vessel for ease of injecting molten ash together with combustion gases into the recovery vessel and to impart anim-' proved fluidity to the molten salts.

The inner surface of the downcomer (18) for the combustion gases isautomatically cooled withthe liquid passing exteriorly ,of said downcomer. Consequently', the ash tends to adhere to said inner surface. For this reason, it is contemplatedthat the water to be supplied to the recovery vessel'be led to the-innerside of the downcomer (18) through header (17) so as to dissolve the salts with water.

The fine particles of sodium carbonate particles which have been meltedand adhered to theinner sur-. face of the furnace, are injected into the recovery ves-.

sel together with the combustiongases via downcomer (18), so that most of thesodium carbonate,or.ash, is I duced into the evaporator for concentrating additional waste.

As a further illustrative example, a system was employed with a 11,000 lbs of waste/hr. The concentration of the solute was 20 percent and-the-major components to be treated were sodium carboxylate and inorganic materials, the lower calorific valuebased onanhydride being 5035 BTU/lb.

In this case, the rate of the steam produced from the recovery vessel was about 11,000 lbs/hr.

During combustion of the concentratedwaste inthe furnace, 2,640 lbs/hr of water corresponding to the enetire water contained in the concentrate was evaporated and the steam to atomize the wasteamountedto l,760 lbs/hr, so that the steam contained inthe exhaust gases discharged from the recovery vessel was 15,000lbs/hr.

sure on the surface of the waste in the evaporatoruas low as to 300 mm/I-Ig abs. For this reasomsteam ejectors (28) and (30) as well as condenser (29) are used. The vacuum devices (27) (30) were watervejec ;v

A volume of steam almost as great asthat Ofwih:

steam liberated from the waste, was produced from the exhaust gases in the evaporator and then discharged into the sewerage (31). In this manner, thewaste from the evaporator was condensed to a 45 percent solution,

and then delivered to thespray nozzle(9)from.storage tank (6).

It will be appreciated that the present invention provides an efficient waste treatment method and system, wherein high temperature combustion exhaust gases are injected into water and the ash produced is recovered in the form of an aqueous solution or a slurry, and,

most important, the heat contained in the waste as well as the heat evolved from the auxiliary fuel are recov-- ered as steam which contains non-condensable gases, whereby the heat of said steam is utilized for concentrating additional waste under a reduced pressure.

What is claimed is: v

1. A method for treating liquid waste, which comprises the steps of a. providing a liquid waste containing a mixture of organic and inorganic or organo-metallic materials, said materials after complete combustion producing an alkalimetal containing ash;

b. concentrating said waste in an evaporator;

c. injecting and atomizing the thus concentrated waste into a vertical furnace through a spray nozzle at the upper portion of said furnace;

d. combusting said injected and atomized waste in said vertical furance at least above 800 C and above the fusionn temperature of the thus produced ash;

e. introducing combustion gases evolved from said vertical furnace into contact with boiling water in a recovery vessel to dissolve and recover said molten ash immediately in the form of solution or slurry;

f. passing combustion gases into said evaporator to utilize the heat contained in said combustion gases.

2. The method as set forth in claim 1, wherein said combustion gases introduced into said evaporator are introduced directly from said furnace and comprise only a part of the total combustion gases produced from said furnace.

3. A system for treating liquid waste which contains a mixture of organic and, inorganic or organo-metallic materials, which comprises.

a. an evaporator for concentrating said liquid waste to produce a first concentrated waste; b. a furnace for combusting said concentrated waste;

c. a spray nozzle on said furnace to spray-injected said first concentrated waste into said furnace to finally concentrate same to a dried material;

d. a burner on the upper portion of said furnace for burning auxiliary combustion fuel;

' e. a recovery vessel to collect the ash contained in the dried material and entrained in the combustion gases evolved from said furance, said gases contacting water in said vessel for dissolution of the dried material;

f. a duct connected at one end to said furance and at the other end to said evaporator, whereby a part of said combustion gases from said furnace are introduced into said evaporator for producing said first concentrate;

g. a means for introducing compressed air to said spray nozzle, to atomize said injected waste and to accelerate the rates of combustion and evaporation thereof to produce said dried material; and

h. a valve means for said recovery vessel and said evaporator to adjust the concentration of concentrated waste by controlling the flow of said combustion gases from said recovery vessel and said evaporator.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,8 +7,7|5 Dated November 12, 197A Inventor(s) Mikio Akune et 1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page at V75]- delete "Kokiohi Yoshii, Shibukawa" at ZZ /correot "Nittelsu" to read Nittetsu-, and "Cheyoda" to read -Chiyoda.

Signed and Scaltd this thirtieth Day of Dcmber1975 [SEAL] Attest:

RUTH C. MASON C. IIAISIIALL DANN Arresting Officer Commissioner a] Portal: and Trademarks 

1. A METHOD FOR TREATING LIQUID WASTE, WHICH COMPRISES THE STEPS OF A. PROVIDING A LIQUID WASTE CONTAINING A MIXTURE OF ORGANIC AND INORGANIC OR ORGANO-METALLIC MATERIALS, SAID MATERIALS AFTER COMPLETE COMBUSTION PRODUCING AN ALKALIMETAL CONTAINING ASH, B. CONCENTRATING SAID WASTE IN AN EVAPORATOR, C. INJECTING AND ATOMIZING THE THUS CONCENTRATED WASTE INTO A VERTICAL FURNACE THROUGH A SPRAY NOZZLE AT THE UPPER PORTION OF SAID FURNACE, D. CUMBUSTING SAID INJECTED AND ATOMIZED WASTE IN SAID VERTICAL FURANCE A AT LEAST ABOVE 800*C AND ABOVE THE FUSIONN TEMPERATURE OF THE THUS PRODUCED ASH, E. INTRODUCING COMBUSTION GASES EVOLVED FROM SAID VERTICAL FURNACE INTO CONTACT WITH BOILING WATER IN A RECOVERY VESSEL TO DISSOLVE AND RECOVER SAID MOLTEN ASH IMMEDIATELY IN THE FORM OF SOLUTION OR SLURRY, F. PASSING COMBUSTION GASES INTO SAID EVAPORATOR TO UTILIZE THE HEAT CONTAINED IN SAID COMBUSTION GASES.
 2. The method as set forth in claim 1, wherein said combustion gases introduced into said evaporator are introduced directly from said furnace and comprise only a part of the total combustion gases produced from said furnace.
 3. A system for treating liquid waste which contains a mixture of organic and inorganic or organo-metallic materials, which comprises: a. an evaporator for concentrating said liquid waste to produce a first concentrated waste; b. a furnace for combusting said concentrated waste; c. a spray nozzle on said furnace to spray-injected said first concentrated waste into said furnace to finally concentrate same to a dried material; d. a burner on the upper portion of said furnace for burning auxiliary combustion fuel; e. a recovery vessel to collect the ash contained in the dried material and entrained in the combuStion gases evolved from said furance, said gases contacting water in said vessel for dissolution of the dried material; f. a duct connected at one end to said furance and at the other end to said evaporator, whereby a part of said combustion gases from said furnace are introduced into said evaporator for producing said first concentrate; g. a means for introducing compressed air to said spray nozzle, to atomize said injected waste and to accelerate the rates of combustion and evaporation thereof to produce said dried material; and h. a valve means for said recovery vessel and said evaporator to adjust the concentration of concentrated waste by controlling the flow of said combustion gases from said recovery vessel and said evaporator. 